For a few fleeting days each spring, there is a moonlight migration in the centre of the city

It goes unnoticed by most, but the march of the toads is a spring spectacle that has just as much drama as any migration story

Waking from winter hibernation, common toads have a sudden urge to make for their ancestral breeding pools

Many will perish whilst crossing seas of tarmac, but they are driven by a desire to pass on their genes to the next generation

In Bristol, a favoured breeding pond is at the crest of its tallest hill, so a heroic ascent must be conquered

At the summit, they wait for darkness to break from cover. The fat females, heavy with eggs haul themselves out to make the final crossing

Progress is often encumbered by amorous males, who clamp themselves on in a powerful embrace, hoping to get a headstart on the competition

At least she will be free from further advances until she reaches the pond - with his arms securely fastened he can fend off rivals with a mighty backwards kick

But most males arrive at the party alone. They reach sexual maturity a year earlier, so can greatly outnumber the females

However they make it and despite all the dangers, thousands of toads will attempt this adventurous annual expedition

As the ultimate reward awaits for those that arrive - the brief opportunity to secure their genetic survival. At least until next year